Enhancing the structural stability and cycling performance of LiCoO2 at 4.55 V by YPO4 modification

To date, LiCoO 2 has received extensive attention as a cathode material because of its unique characteristics. To satisfy the strong demand for high energy density , the cut-off voltage of LiCoO 2 is continuously increased. However, the structural instability of LiCoO 2 at a high cut-off voltage leads to capacity decay and many safety issues, which hinder further application of LiCoO 2 . Herein, YPO 4 is used to achieve a better electrochemical performance for LiCoO 2 at 4.55 V. In the synthesis process, YPO 4 is transformed into the Li 3 PO 4 and Y 2 O 3 phases, which are basically uniformly incorporated into the particle and form a composite with LiCoO 2 . Owing to the synergistic modification of Li 3 PO 4 and Y 2 O 3 phases, YPO 4 -modified LiCoO 2 materials show enhanced structural stability and excellent cycling performance. Particularly, 1.5% YPO 4 modified LiCoO 2 not only exhibits a reversible discharge capacity of 171.6 mAh g −1 over 500 cycles with 91.7% capacity retention, but also delivers a capacity of 144.5 mAh g −1 at 5 C (1 C = 274 mAh g −1 ). This work suggests that using rare-earth metal phosphates can be an effective strategy to improve the cycling performance of LiCoO 2 at 4.55 V.